I don't know for sure since I haven't read it. But it could be a young hero who has the power or determination to slay dragons. Maybe there's also a wise teacher or mentor figure who guides the hero.
In the 'gakuen dragon slayer novel', the main characters might include a student who is an outcast but discovers they have a latent ability to slay dragons. There could be a popular student who initially doubts the existence of dragons but later joins the cause. And of course, there might be an antagonist, perhaps a dragon or a human who is in league with the dragons and tries to stop the main characters from achieving their goal of slaying the dragons.
I'm not entirely sure as I haven't read it in detail. But generally, it might involve a story set in a school (gakuen) and some sort of dragon - slaying elements, perhaps battles against dragons, or a character with the ability to slay dragons within the school environment.
It's possible that there's a love interest for Percy in the fanfiction. This character could be another adventurer or someone from Percy's past. Their relationship could add an emotional aspect to the story, as Percy has to balance his feelings for this person with his dangerous job as a dragon slayer.
In some fanfictions, Happy, the flying cat, could also be an important character. He could provide comic relief and also be involved in some of Lucy's adventures as a dragon slayer. For example, he might help her find clues or get out of difficult situations. And then there could be original characters created specifically for the fanfiction. These characters could be other dragon slayers or powerful mages that interact with Lucy in different ways.
Since I don't have the actual fanfiction, it's hard to say for sure. But it's likely that the dragon slayer is a main character. There could also be other characters like villagers who are being affected by the situation related to 'the nothing' and perhaps other dragon slayers or mentors.
Typically, the main character is the dragon slayer. They are often a brave and determined individual with unique skills and a strong will.
It's hard to say without reading it, but it could be the ice dragon slayer themselves. Maybe there's also a wise mentor figure who guides the slayer.
In some 'hellfire dragon slayer fanfic', there could be a powerful wizard as a main character. This wizard might not be a direct slayer but has the knowledge and power to help the slayer in their quest. And of course, the hellfire dragons can be considered main characters in a way, as their actions and nature drive much of the story's conflict.
Well, Naruto is likely to be one of the main characters. Since it's a Naruto - related fanfiction, he'll probably be at the center of the story. There might also be characters from the dragon slayer world that are important, like the typical dragon slayer mages. But without reading it specifically, it's hard to say exactly who all the main characters are.
In some fanfictions, there might be original characters created by the author. For instance, a mysterious figure who has some connection to Natsu's multi - dragon slayer abilities. This character could be an antagonist, testing Natsu's skills, or a mentor, guiding him to master his powers better.
Obviously, Harry is the main character. He is the one with the dragon - slaying role. But often, his friends like Hermione and Ron might also be involved. They could be helping Harry in his dragon - slaying quests, providing him with magical knowledge or just moral support.